U.S. patent application number 10/649918 was filed with the patent office on 2004-03-11 for mobile communication network system.
Invention is credited to Nakatsugawa, Keiichi, Oka, Kazuyuki.
Application Number | 20040049532 10/649918 |
Document ID | / |
Family ID | 31986265 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040049532 |
Kind Code |
A1 |
Oka, Kazuyuki ; et
al. |
March 11, 2004 |
Mobile communication network system
Abstract
When a failure occurs in a node managing the location
information of mobile node MN, it is possible to resume packet
transfer from correspondent node CN to mobile node MN after the
node is restored from the failure, in a mobile communication
network. The mobile communication network includes a plurality of
nodes including a home agent, a correspondent node, and a mobility
anchor point connected to the network, wherein each node produces a
duplication of a binding cache on receipt of location registration
information from a mobile terminal, maintains and manages the
duplication of the binding cache, and on restoration of the node
from a failure, each node obtains the contents of the binding cache
stored before the node failure from the duplicated binding
cache.
Inventors: |
Oka, Kazuyuki;
(Yokohama-shi, JP) ; Nakatsugawa, Keiichi;
(Kawasaki-shi, JP) |
Correspondence
Address: |
KATTEN MUCHIN ZAVIS ROSENMAN
575 MADISON AVENUE
NEW YORK
NY
10022-2585
US
|
Family ID: |
31986265 |
Appl. No.: |
10/649918 |
Filed: |
August 27, 2003 |
Current U.S.
Class: |
709/202 ;
709/224 |
Current CPC
Class: |
H04W 80/04 20130101;
H04W 24/04 20130101; H04L 69/40 20130101; H04W 8/085 20130101; H04W
8/02 20130101; H04W 4/16 20130101 |
Class at
Publication: |
709/202 ;
709/224 |
International
Class: |
G06F 015/16 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2002 |
JP |
2002-251312 |
Claims
What is claimed is:
1. A mobile communication network system comprising a plurality of
nodes including a home agent, a correspondent node, and a mobility
anchor point connected to the network, wherein each node produces a
duplication of a binding cache on receipt of location registration
information from a mobile terminal, maintains and manages the
duplication of the binding cache, and on restoration of the node
from a failure, each node obtains the contents of the binding cache
stored before the node failure from the duplicated binding
cache.
2. The mobile communication network system according to claim 1,
wherein the node transmits a location registration request to the
mobile terminal in accordance with the contents of the binding
cache obtained before the failure, and when no response is received
against the location registration request, the node determines the
binding cache obtained before the failure as invalid, and deletes
the location information of said mobile terminal.
3. The mobile communication network system according to claim 2,
wherein, when a plurality of mobile terminals exist as objects for
transmitting the location registration request, the node controls
transmission intervals of said location registration requests to
the plurality of mobile terminals by successively transmitting with
delay.
4. A mobile communication network system comprising a plurality of
nodes each connected to the network, wherein, when a mobile
terminal moves from a particular node to another different node,
said mobile terminal obtains from an external link a node address
after the movement as a care-of address, and transmits the obtained
care-of address to the particular node as location registration
information, the particular node registers the location
registration information into a binding cache, manages the location
registration information, duplicates the contents of the binding
cache for backup purpose, and maintains and manages the duplicated
contents of the binding cache, and when the particular node is
restored from a failure and initiated for restoration, the
particular node transmits a location registration request to the
mobile terminal which is registered in the binding cache, and when
no response is received from the mobile terminal against the
location registration request, the node deletes the location
information of the mobile terminal from the binding cache.
5. The mobile communication network system according to claim 4,
wherein the plurality of nodes include a correspondent node and a
home agent, and when the correspondent node transmits a packet to
the mobile terminal using a home address of the mobile terminal,
the home agent transfers the packet to the care-of address
registered in the binding cache.
6. The mobile communication network system according to claim 5,
further comprising a mobility anchor point as one of the plurality
of nodes, wherein the mobile terminal transmits the care-of
address, which is transmitted to the home agent as location
registration information, to the mobility anchor point as location
registration information, and registers the care-of address into a
binding cache of the mobility anchor point.
7. The mobile communication network system according to claim 6,
wherein, when a packet is transmitted from the correspondent node
to the mobile terminal using the home address of the mobile
terminal, the packet is intercepted by the home agent and the
mobility anchor point, and transferred to the mobile terminal.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a mobile communication
network system employing Mobile Internet Protocol (Mobile-IP) ,
having capability of managing the location of a mobile terminal and
recovering the location information.
BACKGROUND OF THE INVENTION
[0002] In an IP network for communication using Internet Protocol,
and further in a mobile communication network using Mobile-IP (MIP.
Refer to HYPERLINK http://www.ietf.org/rfc/rfc3220.txt), a mobile
terminal (hereinafter referred to as mobile node MN) consisting of
a portable personal computer, a portable telephone terminal, or the
like is connected to the Internet through a home agent HA
functioning as a node. In such a network, mobile node MN informs
the corresponding home agent HA about the location information of
each mobile node MN, so that the location of each mobile node is
registered in each home agent HA.
[0003] The location information received from mobile node MN is
maintained and managed in each home agent HA as binding cache BC.
Home agent HA transfers a packet, which is originated in
correspondent node CN and destined for mobile node MN, in
accordance with the contents of binding cache BC.
[0004] When the location of mobile node MN is registered into
correspondent node CN for optimizing the route, correspondent node
CN transmits a packet for transfer directly to mobile node MN of
interest according to binding cache BC.
[0005] The above-mentioned procedure is also applicable in the case
of Mobile-IPv6 (MIPv6. For example, refer to
http://www.ietf.org/internet-dr-
afts/draft-ietf-mobileip-iPv6-18.txt).
[0006] Mobile-IPv6 is a kind of Mobile-IP which is based on
Internet Protocol version 6.
[0007] Further, the above-mentioned procedure is also applicable to
Hierarchical Mobile-IP (HMIP. For example, refer to
http://www.ietf.org/internet-drafts/draft-ietf-mobileip-hmiPv6
-06.txt) and its IPv6 version, Hierarchical Mobile-IPv6 (HMIPv6.
For example, refer to http://www.ietf.org/rfc/rfc2460.txt). These
protocols enable to support high-speed handover by a Mobility
Anchor Point (MAP) , which is implemented in the network to which
the mobile node moves, and acts as a proxy node in place of home
agent HA.
[0008] The following links respectively refer to aforementioned
nonpatent documents:
[0009] In such a mobile communication network, home agent HA acting
as a node, correspondent node CN and mobility anchor point MAP
maintain and manage the location information reported from mobile
node MN as binding cache BC, thus enabling packet transfer from
correspondent node CN to mobile node MN.
[0010] Under such circumstances, when a failure occurs in either
node which retains binding cache BC registered from mobile node MN,
transferring a packet originated in correspondent node CN and
destined for mobile node MN is suspended even when the node of
interest is restored from the failure, unless binding cache BC
having been retained is restored.
[0011] Generally, when a failure occurs in a node retaining binding
cache BC, the restoration of binding cache BC relies on a request
for location re-registration which is to be issued at an arbitrary
timing from mobile node MN. In such a case, a packet originated in
correspondent node CN and destined for mobile node MN possibly
fails to reach the destination, or reaches through an unintended
route (in other words, through a route which is not optimized).
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an object of the present invention to
provide a mobile communication network, so as to solve such
inconvenience explained above.
[0013] In a mobile communication network according to the present
invention to solve the aforementioned problem, each node connected
to the network, including home agent HA, correspondent node CN, and
mobility anchor point MAP, produces a duplication of binding cache
(i.e. binding cache for the backup), and maintains and manages the
duplicated binding cache.
[0014] On restoration from a failure having occurred in either of
the nodes, each node of home agent HA, correspondent node CN, and
mobility anchor point MAP searches the aforementioned backup
binding cache and obtains binding cache BC having been retained
before the failure.
[0015] Further, in order to verify whether the obtained binding
cache BC is valid, each node of interest requests mobile node MN,
of which location has been registered beforehand, to perform
location registration again. In reply to this request, when the
node receives a response of location registration information from
mobile node MN, the node determines that the binding cache BC of
interest is still valid. The node therefore maintains and manages
the location information of mobile node MN in binding cache BC.
[0016] Meanwhile, when the node receives no reply of location
registration information from mobile node MN, the node determines
the binding cache BC of interest is not valid, and therefore the
node deletes binding cache BC.
[0017] Further, when any of home agent HA, correspondent node CN or
mobility anchor point MAP requests mobile node MN to register the
location so as to verify the validity of binding cache BC, and in
case that a plurality of mobile nodes have been registered in the
backup bending cache, the location registration request messages to
be forwarded to the plurality of mobile nodes are controlled to
transmit one after another with delayed transmission intervals, so
as to lessen the load.
[0018] Further scopes and features of the present invention will
become more apparent by the following description of the
embodiments with the accompanied drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows exemplary routes of location registration and
packet transfer after the location registration in conformity with
Mobile-IPv6.
[0020] FIG. 2 shows exemplary routes of location registration and
packet transfer after the location registration as a result of
route optimization in conformity with Mobile-IPv6.
[0021] FIG. 3 shows exemplary routes of location registration and
packet transfer after the location registration as a result of
route optimization in conformity with Hierarchical Mobile-IPv6.
[0022] FIG. 4 shows exemplary routes of location registration and
packet transfer after the location registration as a result of
route optimization, in contrast to the location registration and
packet transfer after the location registration conforming to
Hierarchical Mobile-IPv6 shown in FIG. 3.
[0023] FIG. 5 shows an exemplary format of location registration
information.
[0024] FIG. 6 shows a diagram illustrating an example of failure
occurrence in home agent HA in the case of Mobile-IPv6.
[0025] FIG. 7 shows a diagram illustrating an example of failure
occurrence in correspondent node CN in the example while route
optimization is being registered in the case of Mobile-IPv6 shown
in FIG. 2.
[0026] FIG. 8 shows a diagram illustrating an example of failure
occurrence in home agent HA in the case of Hierarchical Mobile-IPv6
shown in FIG. 3.
[0027] FIG. 9 shows a diagram illustrating an example of failure
occurrence in mobility anchor point MAP in the case of Hierarchical
Mobile-IPv6 shown in FIG. 3.
[0028] FIG. 10 shows a diagram illustrating an example of failure
occurrence in mobility anchor point MAP while route optimization
shown in FIG. 4 is performed, in the case of Hierarchical
Mobile-IPv6.
[0029] FIG. 11 shows an embodiment of the present invention.
[0030] FIG. 12 shows a diagram illustrating that home agent HA, on
restoration from a failure, starts maintenance and management of
binding cache BC after identifying the validity of binding cache BC
concerned.
[0031] FIG. 13 shows a functional diagram of an exemplary
configuration of home agent HA.
[0032] FIG. 14 shows a processing flowchart corresponding to FIG.
13.
[0033] FIG. 15 shows a diagram illustrating a message format of a
location registration request.
[0034] FIG. 16 shows an operation of home agent HA performed when
receiving location registration information from mobile node MN in
response to a location registration request sent from home agent
HA.
[0035] FIG. 17 shows a processing flowchart corresponding to FIG.
16.
[0036] FIG. 18 shows a diagram illustrating a procedure of deleting
the location information in backup binding cache BC in the case of
Mobile-IPv6.
[0037] FIG. 19 shows a diagram illustrating a case that a location
registration request from home agent HA cannot be received because
mobile node MN has moved onto another link before home agent HA is
restored.
[0038] FIG. 20 shows a timing chart corresponding to FIG. 19.
[0039] FIG. 21 shows a diagram (part 1) illustrating an exemplary
recovery operation of binding cache BC performed in correspondent
node CN in the case of Mobile-IPv6.
[0040] FIG. 22 shows a diagram (part 2) illustrating the exemplary
recovery operation of binding cache BC performed in correspondent
node CN in the case of Mobile-IPv6.
[0041] FIG. 23 shows a diagram (part 3) illustrating the exemplary
recovery operation of binding cache BC performed in correspondent
node CN in the case of Mobile-IPv6.
[0042] FIG. 24 shows a diagram (part 1) illustrating an exemplary
recovery operation of binding cache BC performed in mobility anchor
point MAP in the case of Hierarchical Mobile-IPv6.
[0043] FIG. 25 shows a diagram (part 2) illustrating an exemplary
recovery operation of binding cache BC performed in mobility anchor
point MAP in the case of Hierarchical Mobile-IPv6.
[0044] FIG. 26 shows a diagram (part 3) illustrating an exemplary
recovery operation of binding cache BC performed in mobility anchor
point MAP in the case of Hierarchical Mobile-IPv6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] The preferred embodiments of the present invention will be
described hereinafter referring to the charts and drawings.
However, prior to the description of the embodiment, problems in
the conventional mobile communication network, which lie as the
prerequisites against the issues of the present invention, are
studied further for easy understanding of the present
invention.
[0046] FIG. 1 shows exemplary routes for use in location
registration and packet transfer after location registration in
conformity with Mobile-IPv6. In this figure, R1-R4 respectively
denote routers. Each router belongs to each of the networks which
are interconnected through the Internet 100.
[0047] In FIG. 1, a mobile node MN has moved to a network area
having router R3 from a home network location in which a home agent
HA manages the registration location in a network area having
router R2. In this situation, mobile node MN obtains a care-of
address (CoA) through an external link by the use of a `Router
Advertisement` message which is periodically issued from router R3
located in the network area to which mobile node MN moved.
[0048] Thereafter mobile node MN transmits the location
registration information to home agent HA (step {circle over
(1)}).
[0049] On receipt of the location registration information from
mobile node MN, home agent HA manages the location information as
binding cache BC (step {circle over (2)}). Here, both the home
address (HoA) of mobile node MN and the care-of address (CoA) of
mobile node MN are included in the location registration
information sent from mobile node MN.
[0050] Meanwhile, correspondent node CN transmits packets destined
for mobile node MN to the home address (HoA) of mobile node MN when
correspondent node CN has not recognized that mobile node MN
already moved (step {circle over (3)}).
[0051] Home agent HA handles the packet received from correspondent
node CN as a packet to be destined for mobile node MN of which
information is retained in binding cache BC. Accordingly, home
agent HA transfers the packet to the care-of address (CoA)
according to binding cache BC after encapsulating the packet of
interest (step {circle over (4)}).
[0052] In such a way, even when mobile node MN has moved from the
home address (HoA) to the care-of address (CoA), mobile node MN can
receive the packet destined therefor transmitted from correspondent
node CN which does not recognize mobile node MN has moved.
[0053] FIG. 2 shows exemplary routes for use in location
registration and packet transfer after location registration as a
result of route optimization in conformity with Mobile-IPv6. In
this figure, as well as the succeeding figures, the connection
between each node and the Internet is omitted for simplification,
as it is identical to FIG. 1.
[0054] In a similar manner to FIG. 1, when mobile node MN has moved
from the location in the home network area having router R2, mobile
node MN determines whether route optimization is to perform. When
deciding to perform the route optimization, mobile node MN
transmits the location registration information to correspondent
node CN (step {circle over (1)}-1).
[0055] On receipt of the location registration information from
mobile node MN, correspondent node CN manages the location
information as binding cache BC (step {circle over (2)}-1) When
correspondent node CN is to transmit a packet to mobile node MN,
correspondent node CN transmits the packet of interest to the
care-of address (CoA) according to binding cache BC (step {circle
over (3)}-1). In this case shown in FIG. 2, it becomes possible to
transmit a packet from correspondent node CN directly to mobile
node MN, without interception by home agent HA. This enables to
omit packet processing in home agent HA, which results in making
the processing time shorter as well as achieving the route
optimization.
[0056] Further, FIG. 3 shows exemplary routes of location
registration and packet transfer after the location registration in
conformity with Hierarchical Mobile-IPv6.
[0057] In the case of Hierarchical Mobile-IPv6, when mobile node MN
moves, mobile node MN obtains both an on-link care-of address
(LCoA) and a regional care-of address (RCoA) through an external
link. Mobile node MN then transmits to mobility anchor point MAP
the location registration information by the use of the on-link
care-of address (LCoA) as the location information (step {circle
over (1)}-2).
[0058] On receipt of the location registration information from
mobile node MN, mobility anchor point MAP manages the location
information as binding cache BC (step {circle over (2)}-2).
[0059] After transmitting the location registration information to
mobility anchor point MAP, mobile node MN also transmits location
registration information to home agent HA (step {circle over
(3)}-2). At this time, the regional care-of address (RCoA) is used
as the location information.
[0060] On receipt of the location registration information from
mobile node MN, home agent HA manages the location information as
binding cache BC (step {circle over (4)}-2).
[0061] Here, when correspondent node CN has not recognized the
movement of mobile node MN, correspondent node CN transmits a
packet to the home address (HoA) of mobile node MN (step {circle
over (5)}-2).
[0062] Home agent HA receives the packet as a packet destined for
mobile node MN the information of which is retained in binding
cache BC. After encapsulating the packet of interest, home agent HA
transfers the encapsulated packet to the regional care-of address
(RCoA) according to binding cache BC (step {circle over
(6)}-2).
[0063] On receipt of the encapsulated packet destined for the
regional care-of address (RCoA) , mobility anchor point MAP
decapsulates (removes the capsulation of) the received packet, and
then recognizes the packet to be destined for mobile node MN the
information of which is retained in binding cache BC. Further
mobility anchor point MAP transfers the packet to the care-of
address (CoA) according to binding cache BC after encapsulating the
packet concerned (step {circle over (7)}-2).
[0064] FIG. 4 shows exemplary routes of location registration and
packet transfer after the location registration as a result of
route optimization conforming to Hierarchical Mobile-IPv6, in
contrast to the location registration and packet transfer after the
location registration shown in FIG. 3.
[0065] Mobile node MN determines whether route optimization is to
perform. When performing the route optimization, mobile node MN
transmits the location registration information to correspondent
node CN (step {circle over (1)}-3). At this time, the regional
care-of address (RCoA) is used as the location information. On
receipt of the location registration information from mobile node
MN, correspondent node CN manages the location information as
binding cache BC (step {circle over (2)}-3).
[0066] When transmitting a packet to mobile node MN, correspondent
node CN transmits the packet to the care-of address (CoA) according
to binding cache BC (step {circle over (3)}-3). Mobility anchor
point MAP then receives the packet destined for the regional
care-of address (RCoA), and recognizes the packet to be destined
for mobile node MN the information of which is retained in binding
cache BC. After encapsulating the packet, mobility anchor point MAP
transfers the encapsulated packet to the care-of address (CoA)
according to binding cache BC (step {circle over (4)}-3).
[0067] In relation to the above description, FIG. 5 shows an
exemplary format of the aforementioned location registration
information to be transmitted from mobile node MN to either home
agent HA or correspondent node CN. The format shown in FIG. 5 is a
format conforming to IPv6, in which only a header part is shown.
The header part includes an IPv6 header I, and a destination option
header II. IPv6 header I further is constituted of a source IP
address (I-1) and a destination IP address (I-2).
[0068] As source IP address (I-1), there is specified the care-of
address (CoA), which is the address on the link onto which mobile
node MN moved, consisting of a network address and a host address.
Destination IP address (I-2) is any one of the home address (HoA)
of home agent HA, the address of correspondent node CN, or the
address of mobility anchor point MAP, depending on the destination
of the location registration information.
[0069] Destination option header II includes, as registration
information, a flag II-1, a life time II-2 of binding cache BC, in
other words, a retention period of the registration information,
and a home address (HoA) II-3 which is the address of mobile node
MN on the home link. This home address (HoA) is used as a key when
searching backup binding cache BC.
[0070] Here, as shown in FIGS. 1 through 4, in Mobile IP (which
includes Mobile-IPv6, Hierarchical Mobile-IP, and Hierarchical
Mobile-IPv6) , home agent HA, correspondent node CN and mobility
anchor point MAP maintain and manage the location information sent
from mobile node MN as binding cache BC, thus enabling packet
transfer from correspondent node CN to mobile node MN.
[0071] In such situations as mentioned above, when a failure occurs
in any node retaining binding cache BC registered from mobile node
MN, and even after the node of interest is restored from the
failure, it becomes unable to perform packet transfer from
correspondent node CN to mobile node MN unless binding cache BC
which was retained before is restored.
[0072] In general, the restoration timing of this binding cache BC
relies on a request for location re-registration issued at an
arbitrary timing from mobile node MN.
[0073] FIG. 6 shows an exemplary case when a failure occurs in home
agent HA in conformity with Mobile-IPv6.
[0074] On occurrence of the failure in home agent HA, binding cache
BC having been maintained and managed is lost, and thereafter, home
agent HA is restored from the failure (step ({circle over (1)}-4).
Correspondent node CN transmits a packet to the home address (HoA)
of mobile node MN because correspondent node CN does not retain
binding cache BC for route optimization (step {circle over
(2)}-4).
[0075] Because binding cache BC has been lost in home agent HA, it
is not possible for home agent HA to transfer the packet originated
in correspondent node CN and destined for the home address (HoA) of
mobile node MN to the location onto which mobile node MN has moved
(step {circle over (3)}-4).
[0076] FIG. 7 shows an exemplary case when a failure occurs in
correspondent node CN while route optimization shown in FIG. 2 is
being registered in conformity with Mobile-IPv6. On occurrence of
the failure in correspondent node CN, binding cache BC having been
maintained and managed is lost, and thereafter, correspondent node
CN is restored from the failure (step {circle over (1)}-5).
[0077] Correspondent node CN transmits a packet to the home address
(HoA) of mobile node MN, because correspondent node CN does not
retain binding cache BC for route optimization (step {circle over
(2)}-5). In FIG. 7, home agent HA transfers the packet to the
care-of address (CoA) of mobile node MN (step {circle over (3)}-5).
Accordingly, although the packet originated in correspondent node
CN and destined for mobile node MN reaches mobile node MN, the
intended route optimization does not take place.
[0078] FIG. 8 shows an exemplary case when a failure occurs in home
agent HA in conformity with Hierarchical Mobile-IPv6 shown in FIG.
3. On occurrence of the failure in home agent HA, binding cache BC
having been maintained and managed is lost, and thereafter, home
agent HA is restored from the failure (step {circle over
(1)}-6).
[0079] Correspondent node CN transmits a packet to the home address
(HoA) of mobile node MN, because correspondent node CN does not
retain binding cache BC for route optimization (step {circle over
(2)}-6).
[0080] Because binding cache BC has been lost in home agent HA, it
is not possible for home agent HA to transfer the packet originated
in correspondent node CN and destined for the home address (HoA) of
mobile node MN to the location to which mobile node MN has moved
(step {circle over (3)}-6).
[0081] FIG. 9 shows an exemplary case when a failure occurs in
mobility anchor point MAP in conformity with Hierarchical
Mobile-IPv6 shown in FIG. 3. In this example, correspondent node CN
does not retain binding cache BC for route optimization.
[0082] On occurrence of the failure in mobility anchor point MAP,
binding cache BC having been maintained and managed is lost, and
thereafter, mobility anchor point MAP is restored from the failure
(step {circle over (1)}-7)
[0083] Correspondent node CN transmits a packet to the home address
(HoA) of mobile node MN, because correspondent node CN does not
retain binding cache BC for route optimization (step {circle over
(2)}-7).
[0084] After encapsulating the received packet, home agent HA
transfers the packet destined for the home address (HoA) of mobile
node MN to the care-of address (CoA) in accordance with binding
cache BC (step {circle over (3)}-7).
[0085] However, because binding cache BC has been lost in mobility
anchor point MAP, it is not possible for mobility anchor point MAP
to transfer the packet transmitted from home agent HA to the
location to which mobile node MN has moved (step {circle over
(4)}-7).
[0086] FIG. 10 shows an exemplary case when a failure occurs in
mobility anchor point MAP while route optimization shown in FIG. 4
is being performed in conformity with Hierarchical Mobile-IPv6. In
this example, correspondent node CN retains binding cache BC for
route optimization.
[0087] On occurrence of the failure in mobility anchor point MAP,
binding cache BC having been maintained and managed is lost.
Thereafter, mobility anchor point MAP is restored from the failure
(step {circle over (1)}-8).
[0088] Correspondent node CN transmits a packet to the care-of
address (CoA) of mobile node MN in accordance with binding cache
BC, because correspondent node CN retains binding cache BC for
route optimization (step {circle over (2)}-8).
[0089] Because binding cache BC has been lost in mobility anchor
point MAP, it is not possible for mobility anchor point MAP to
transfer the packet transmitted from correspondent node CN to the
location to which mobile node MN has moved (step {circle over
(3)}-8).
[0090] As having been illustrated in FIGS. 6 through 10, when a
failure occurs in any node which retains binding cache BC, a packet
originated in correspondent node CN and destined for mobile node MN
does not reach the destination, or otherwise reaches through an
unintended route (that is, a route without optimization).
[0091] In addition, restoration timing of binding cache BC depends
on a request for location re-registration issued from mobile node
MN at arbitrary timing.
[0092] In consideration of the above-mentioned inconvenience,
according to the present invention, it is intended to eliminate
such inconvenience when a failure occurs in any node. The
embodiment of the present invention is described in the
following.
[0093] FIG. 11 shows an embodiment of the present invention. One
feature of the present invention is that home agent HA is provided
with a procedure of duplicating binding cache BC from mobile node
MN to a backup binding cache BC.
[0094] In FIG. 11, when mobile node MN moves, mobile node MN
obtains the care-of address (CoA) from an external link by the use
of a `Router Advertisement` message which is periodically issued
from router R3. Mobile node MN then transmits location registration
information using the format shown in FIG. 5 (step {circle over
(1)}-9).
[0095] Home agent HA, on receipt of the location registration
information from mobile node MN, manages the location information
as binding cache BC. At this time, home agent HA also duplicates
binding cache BC for backup purpose (step {circle over (2)}-9).
[0096] FIG. 12 shows an exemplary case that a failure occurs in
home agent HA, and that, on restoration from a failure, home agent
HA starts maintenance and management processing of binding cache BC
after identifying the validity of the binding cache BC. In this
processing, the duplication of binding cache BC shown in FIG. 11 is
used.
[0097] FIG. 13 shows a functional diagram of an exemplary
configuration of home agent HA. Home agent HA is provided with
mobile node manager 1, binding cache 2, backup binding cache 3, and
work table 4. Mobile node manager 1 further includes a binding
cache corrector 10 and a location information manager 11.
[0098] Further, FIG. 14 shows a processing flowchart corresponding
to FIG. 13. In FIG. 12, it is assumed that a failure occurs in home
agent HA (step {circle over (1)}-10). When home agent HA is
restored from the failure and restarted (procedure P1), binding
cache corrector 10 searches backup binding cache 3 to find out
whether location information is stored (procedure P2).
[0099] When it is found that location information is stored in
backup binding cache (BC) 3 (`Y` in procedure P2), the location
information is duplicated into work table 4 (procedure P3).
Thereafter, work table 4 is randomly reshuffled with each prefix of
the care-of address (CoA) handled as a key (procedure P4).
[0100] When the entire location information in backup binding cache
(BC) 3 is duplicated and stored into work table 4 through these
procedures P2 to P4, table 4 is searched (procedure P5).
[0101] A request is issued to location information manager 11 to
transmit a request for location registration to mobile node MN
corresponding to the location information in work table 4
(procedure P6). Location information manager 11 then transmits a
location registration request (procedure P7: step {circle over
(2)}-10). At this time, a timer to wait for reception of location
registration is initiated (procedure P8).
[0102] If a plurality of mobile nodes MN are included in work table
4, transmission intervals of the location registration requests are
controlled to produce delay on a mobile node basis, so as to avoid
excessive load increase in both the node concerned and the network
to which the requests are transmitted (procedure P9).
[0103] Here, the location registration request transmitted from
home agent HA is performed by the use of an exemplary message
format of a location registration request shown in FIG. 15. As
compared with the format of the location registration message from
mobile node MN shown in FIG. 5, there is added a route control
header III. In this case, as mobile node MN is located on the
route, the home address (HoA) of mobile node MN is inserted into
route control header III.
[0104] On receipt of the location registration request from home
agent HA, mobile node MN transmits the location registration
information to home agent HA (step {circle over (3)}-10).
[0105] FIG. 16 shows an operation of home agent HA when receiving
location registration information from mobile node MN in response
to a location registration request from home agent HA. Also, FIG.
17 shows a processing flowchart corresponding to FIG. 16.
[0106] When home agent HA receives the location registration
information from mobile node MN (procedure P10), home agent HA
cancels the timer waiting for reception of the location
registration (procedure P 11). Home agent HA then starts to
maintain and manage the location information in location
information manager 11 after registering the location information
into binding cache (BC) 2 (procedure P12). At this time, location
information manager 11 requests binding cache corrector 10 to
duplicate binding cache 2 and stores into backup binding cache 3
(procedure P13). Thus binding cache BC is duplicated (procedure
P14).
[0107] FIG. 18 shows a procedure of deleting the location
information in backup binding cache BC in the case of Mobile-IPv6,
when home agent HA is restored from the failure having occurred
therein and identifies binding cache BC invalid as a result of
investigating the validity of binding cache BC.
[0108] This situation of deleting the location information stored
in backup binding cache BC occurs, for example, when mobile node MN
cannot receive a location registration request from home agent HA
because mobile node MN has moved onto another link before home
agent HA is restored.
[0109] FIG. 19 illustrates the situation mentioned above. FIG. 20
shows a timing chart corresponding to FIG. 19. Namely, when home
agent HA is restored from the failure (step {circle over (1)}-11),
home agent HA transmits a location registration request to the
care-of address of mobile node MN in accordance with binding cache
BC having been registered before (step {circle over (2)}-11). When
mobile node MN has already moved to another link area (step {circle
over (3)}-11), mobile node MN cannot receive this location
registration request. This produces expiration of the timer waiting
for the location registration reception in location information
manager 11 (procedure P20). Location information manager 11 then
requests binding cache corrector 10 to delete the registered
location information (procedure P21). As a result, backup binding
cache 3 is deleted (procedure P22).
[0110] FIGS. 21 through 23 show diagrams illustrating an exemplary
recovery operation of binding cache BC performed in correspondent
node CN in the case of Mobile-IPv6. Actual operation flow is
similar to the aforementioned case of performing location
registration into home agent HA. Therefore, only the outline of the
flow will be described below.
[0111] In FIG. 21, when mobile node MN moves, mobile node MN
obtains the care-of address (CoA) on an external link by the use of
a `Router Advertisement` message which is periodically issued by
router R3. Mobile node MN then transmits location registration
information to correspondent node CN using the format shown in FIG.
5 (step {circle over (1)}-12).
[0112] On receipt of the location registration information from
mobile node MN, correspondent node CN manages the location
information as binding cache BC. At this time, correspondent node
CN duplicates binding cache BC for backup purpose (step {circle
over (2)}-12).
[0113] Referring to FIG. 22, a failure is assumed to have occurred
in correspondent node CN. When correspondent node CN is restored
from the failure and is restarted (step {circle over (1)}-13), a
location registration request is transmitted from correspondent
node CN (step {circle over (2)}-13). At this time, a timer to wait
for reception of the location registration is initiated.
[0114] Here, the location registration request transmitted from
correspondent node CN is performed by the use of an exemplary
message format for a location registration request shown in FIG.
15. On receipt of the location registration request from
correspondent node CN, mobile node MN transmits the location
registration information to correspondent node CN (step {circle
over (3)}-13) On receipt of the location information from mobile
node MN, correspondent node CN cancels the timer waiting for
reception of the location registration, and starts to maintain and
manage the location information in location information manager 11
by registering the location information in binding cache (BC) 2. At
this time, correspondent node CN duplicates binding cache BC and
stores into the backup binding cache (step {circle over
(4)}-13).
[0115] Thus, correspondent node CN can transmit a packet directly
to mobile node MN using the backup binding cache without
interception by home agent HA (step {circle over (5)}-13).
[0116] FIG. 23 shows a process when correspondent node CN is
restored from the failure having occurred therein and starts to
maintain and manage binding cache BC, using the duplication of
binding cache BC shown in FIG. 21, after identifying the validity
of the binding cache BC. In particular, the figure shows a case in
which the location registration request from correspondent node CN
is unable to receive, because mobile node MN has moved onto another
link before correspondent node CN is restored.
[0117] In FIG. 23, when correspondent node CN is restored (step
{circle over (1)}-14), correspondent node CN transmits a location
registration request to the care-of address of mobile node MN in
accordance with binding cache BC having been registered before
(step {circle over (2)}-14). When mobile node MN has already moved
to another link area (step {circle over (3)}-14), mobile node MN
cannot receive the location registration request. This produces
expiration of the timer waiting for the location registration
reception in location information manager 11. As a result, backup
binding cache 3 is deleted (step {circle over (4)}-14).
[0118] FIGS. 24 through 26 show diagrams illustrating an exemplary
recovery operation of binding cache BC performed in mobility anchor
point MAP in the case of Hierarchical Mobile-IPv6. Actual operation
flow is similar to the aforementioned case of performing location
registration into home agent HA. Therefore, only the outline of the
flow will be described below.
[0119] In FIG. 24, when mobile node MN moves, mobile node MN
obtains the care-of address (CoA) on an external link by the use of
a `Router Advertisement` message which is periodically issued by
router R3. Mobile node MN then transmits location registration
information to mobility anchor point MAP using the format shown in
FIG. 5 (step {circle over (1)}-15).
[0120] At the same time, mobile node MN also transmits the location
registration information to home agent HA (step {circle over
(2)}-15).
[0121] When mobility anchor point MAP receives the location
registration information from mobile node MN, mobility anchor point
MAP manages the location information as binding cache BC. At this
time, mobility anchor point MAP duplicates binding cache BC for
backup purpose (step {circle over (3)}-15).
[0122] Similarly, in home agent HA, binding cache BC is duplicated
when the location registration information is received from mobile
node MN (step {circle over (4)}-15).
[0123] Referring to FIG. 25, a failure is assumed to have occurred
in mobility anchor point MAP. When mobility anchor point MAP is
restored from the failure and is restarted (step {circle over
(1)}-16), a location registration request is transmitted from
mobility anchor point MAP (step {circle over (2)}-16). At this
time, a timer to wait for reception of the location registration is
initiated.
[0124] Here, the location registration request transmitted from
mobility anchor point MAP is also performed by the use of an
exemplary message format for a location registration request shown
in FIG. 15. On receipt of the location registration request from
mobility anchor point MAP, mobile node MN transmits the location
registration information to mobility anchor point MAP (step {circle
over (3)}-16).
[0125] On receipt of the location information from mobile node MN,
mobility anchor point MAP cancels the timer waiting for reception
of the location registration. Mobility anchor point MAP then starts
to maintain and manage the location information in location
information manager 11 after the location information is registered
in binding cache (BC) 2. At this time, mobility anchor point MAP
duplicates binding cache BC for backup purpose (step {circle over
(4)}-16).
[0126] When correspondent node CN intends to transmit a packet to
mobile node MN, correspondent node CN transmits the packet to the
home address (HoA) of mobile node MN (step {circle over (5)}-16).
Home agent HA then transfers the packet to the address of mobility
anchor point MAP in accordance with binding cache BC (step {circle
over (6)}-16). Thereafter, it is possible for mobility anchor point
MAP to transmit the packet to mobile node MN by the use of backup
binding cache (step {circle over (7)}-16).
[0127] FIG. 26 shows a process when mobility anchor point MAP is
restored from the failure which has occurred therein. Mobility
anchor point MAP starts to maintain and manage binding cache BC
using the duplication of binding cache BC shown in FIG. 25, after
the validity of binding cache BC is identified.
[0128] In particular, this case shows that mobile node MN cannot
receive the location registration request from mobility anchor
point MAP, because mobile node MN has moved onto another link
before mobility anchor point MAP is restored.
[0129] In FIG. 26, when mobility anchor point MAP is restored (step
{circle over (1)}-17), mobility anchor point MAP transmits a
location registration request to the care-of address of mobile node
MN in accordance with binding cache BC having been registered
before (step {circle over (2)}-17). When mobile node MN has already
moved to another link area (step {circle over (3)}-17), mobile node
MN cannot receive the location registration request. This produces
expiration of the timer waiting for the location registration
reception in location information manager 11. Accordingly, backup
binding cache 3 is deleted (step {circle over (4)}-17).
[0130] As can be understood from the above description, according
to the present invention, when a failure occurs in a node managing
the location information of mobile node MN, it is possible to
resume packet transfer from correspondent node CN to mobile node MN
after the node is restored from the failure. Moreover, there is no
need of waiting for the location re-registration which is to be
initiated by mobile node MN. Accordingly, it becomes possible to
reduce packet transfer loss from one mobile node MN to another.
[0131] The foregoing description of the embodiments is not intended
to limit the invention to the particular details of the examples
illustrated. Any suitable modification and equivalents may be
resorted to the scope of the invention. All features and advantages
of the invention which fall within the scope of the invention are
covered by the appended claims.
* * * * *
References